1. Field of the Invention
The invention concerns an interferometric measuring process for absolute measurements, in particular for absolute distance measurements, employing a laser which can be tuned without mode-jumping in at least one wavelength range and a suitable laser interferometer configuration for the measuring process in accordance with one of the preceding claims, incorporating a laser which is tunable without mode-jumping in at least one wavelength range.
2. Description of the Prior Art
A device for measuring the distance of an object via the use of a laser beam, consisting of a measuring interferometer and a reference interferometer, is known from DE-PS 36 08 075. Both interferometers are supplied with the beam from the same laser. By means of frequency modulation of the laser beam, a so-called reference beat wave is generated from each 2 mutually interfering component beams, whereby the respective numbers of waves in the measuring beat wave and the reference beat wave are determined using a measuring device, and the measured distance is determined on the basis of the ratio between the numbers of these waves and the known reference distance.
One disadvantage of this process is that the phase of the reference beat wave cannot be determined at a resolution greater than approximately 1/10 of the total wavelength of the beat wave. This resolution falls well short of the resolutions attainable with other methods. A further disadvantage of this process is that it is unsuitable for measured distances which vary in an extreme range. However, this requirement is often relevant for plant control systems in production processes, for example.